With respect to friction drive belts such as V-ribbed belts, various techniques have conventionally been proposed to reduce slip noise or other noise that are produced on pulleys during running of the belts.
For example, Patent Document 1 discloses that powder such as talc powder is caused to adhere to the surfaces of V-shaped ribs of a V-ribbed belt after vulcanization-molding of the V-ribbed belt.
Patent Document 2 discloses that short fibers are provided so as to partially protrude from the surfaces of V-shaped ribs of a V-ribbed belt, and powder such as talc powder is caused to adhere to the surfaces of the V-shaped ribs such that the protruding portions of the short fibers are buried under the talc powder.
Patent Document 3 discloses that a V-ribbed belt having short fibers firmly adhering to the surfaces of V-shaped ribs is manufactured by applying an adhesive to the surface of a vulcanization-molded belt sleeve, and spraying the short fibers on the applied adhesive.
Patent Document 4 discloses that a V-ribbed belt having short fibers adhering to the surfaces of V-shaped ribs is manufactured by applying an adhesive to the inner peripheral surface of an outer mold which has a pattern of the V-shaped ribs formed thereon, and spraying the short fibers on the applied adhesive, while setting a non-crosslinked rubber composition and a cord on an inner mold.
However, a V-ribbed belt having powder such as talc powder which has been sprayed and adheres to the surfaces of V-shaped ribs has a disadvantage: The power adhering to the V-shaped rib surfaces falls off in a short time due to contact with pulleys in running of the belt. In particular, when the belt gets wet in the rain for example, water flow considerably easily causes the powder to fall off the V-shaped rib surfaces, thereby eliminating the noise prevention effect of the powder.
In view of this, Patent Document 5 proposes a V-ribbed belt whose pulley contact-side surfaces of ribs are covered with a powder layer which is combined and integrated with the pulley contact-side surfaces.